what is the internet?silenok.com/content/webunderlyingprinciples.pdf · 2012-07-19 · • netscape...
TRANSCRIPT
What is the Internet?
Elena Silenok @silenok
Questions? Just Raise Your Hand
WWW != Internet
• One of 65,535 possible services on the Internet (email, ftp, telnet, IM, etc.)
• Developed as a way of posting formatted documents online at CERN
• 1993 - Marc Andreessen adds pictures to web display
Sir Tim Berners-Lee Concept (1989)
August 6, 1991
• First web browser/editor
• First web server (NeXT computer)
• First web pages - described the project itself (alt.hypertext newsgroup)
• URL, URI, HTML, HTTP
Mosaic (1993)
Netscape (1994)
1990s
• Netscape IPO - 1995
• Internet Explorer - 1995
• Browser wars - Netscape free in 1998, acquired by AOL
• Antitrust - DoJ vs Microsoft in 1998
• AOL sues Microsoft, gets $750 million, IE royalty-free for 7 years (2003)
How It Works
• User types URL (www.google.com)
• IP address lookup in DNS (74.125.226.180)
• HTTP GET request to 74.125.226.180
• HTTP response + content
• Web browser parses the HTML
HTTP response/request
GET /index.html HTTP/1.1 Host: www.example.com
HTTP/1.1 200 OK Date: Mon, 23 May 2005 22:38:34 GMT Server: Apache/1.3.3.7 (Unix) (Red-Hat/Linux) Last-Modified: Wed, 08 Jan 2003 23:11:55 GMT Etag: "3f80f-1b6-3e1cb03b" Accept-Ranges: bytes Content-Length: 438 Connection: close Content-Type: text/html; charset=UTF-8
HTML
<html><head><title>My web page about World Wide Web</title></head><body><p>The <b>World Wide Web</b>, abbreviated as <b>WWW</b> and ...</p></body></html>
• HyperText Markup Language
• Tags - <img>, <a href>, <div>, <em>, <script>
• Structure and interpretation of a hypertext doc
CSS• Cascading Style sheets
• Describes presentation of a document
• Separates doc content from presentation
• Introduced in 1996, about 2/3 pages in 2008<html><head><style>body {font-size:100%;}h1 {font-size:2.5em;}</style></head><body><h1>This is heading 1</h1></body></html>
HTTP/HTTPS• HTTP is sent plain text; unsecured
• HTTP subject to man-in-the-middle and eavesdropping attacks
• HTTPS = HTTP + SSL/TLS protocol
• Secure channel over an insecure network
• Relies on server certificates/authorities
• Developed in 1994 by Netscape
Statistics
• At least 13.15 billion pages
• Over 1 trillion unique URLs
• As of May 2009, over 109.5 million websites
• 74% are in .com domain
Security
• Worms/Viruses/Trojans
• Social phishing/engineering
• SQL injection
• Cross-Site Scripting (XSS)
• Wireless security - often unencrypted
Firewall
User-side protection
• Do not open attachments that look suspicious
• Type in the website URL manually
• Only run software/visit websites you trust
• Update your software/OS/antivirus regularly
• Use a firewall (especially on a PC)
• Firewall / Antivirus / Adware removal
